Insulated device diagnosing system for diagnosing device based upon partial discharge signal data analyzed by frequency

ABSTRACT

An insulated device diagnosing system is capable of judging the deterioration, lifetime, and defects of a device. The intensity at each voltage phase angle is measured at a plurality of specific frequencies, taking high voltage phase angles as the abscissas. The deterioration, lifetime, and the kind and extent of abnormality of the device are judged from the pattern and intensity of the spectral distribution, which is obtained by peak-holding the measured intensity for a defined time period. According to the present invention, partial discharge can be measured highly sensitively and precisely to diagnose the deterioration, lifetime and the extent of defect of the device. As a result, the insulation reliability of the device can be improved, and the part of the device that should be repaired/replaced can be grasped before disassembly of the device, thereby cutting the maintenance cost.

BACKGROUND OF THE INVENTION

In recent years, substation facilities have had to be strengthened asthe power facilities have been installed at remote places or as thesupply of power to cities has increased. For these necessities, therehave already been spread and serviced gas insulated devices such asso-called gas-insulated breakers or transformers in which a substationdevice such as a disconnector or breaker is housed in a closed containerby using SF₆ gas, which is excellent in insulation and arc extinguishingability to improve the environmental adaptation and to decrease theinstallation volume per kV A. This gas-insulated device is advantageousin its compactness and in its elimination of the exposed charging unitof a grounded tank, but is defective in difficulty of diagnosis for themaintenance attributed to high performance, the increase in the timeperiod for the maintaining and repairing works, and the marked loweringof the insulation reliability when the inside becomes abnormal. Similarproblems are caused in transformers using oil insulation or in cablesusing solid insulation by the increase in the size of the device or inthe transmission distance.

In order to improve the insulation reliability of the insulated devicein its entirety, therefore, a variety of efforts have been madeconventionally for appropriate design/manufacture of the device. For oneimprovement in the capacity of the power supply, confirmation andmonitoring of the reliability of the entire device are required andvarious studies and investigations have been made.

One cause of the lowering of the insulation reliability is thenon-uniform electric field. Especially, SF₆ gas, used in the gasinsulated device, exhibits especially excellent insulatingcharacteristics in a non-uniform electric field, but the insulatingcharacteristics drop extremely under the non-uniform electric field. Thefactors disturbing the field distribution in a gas insulating device canbe defects such as flaws in the surface of high-voltage conductors ormetal foreign matter having entered the inside during assembly ortransportation. Other conceivable factors may be an imperfect contact ofhigh-voltage conductors due to assembly mistakes or defects such asvoids in the insulation spacer. If a non-uniform electric field isestablished in the gas insulating device by those defects, partialdischarge may be caused during the operation, leading to a serioussituation such as the breakdown of the entire circuit. This makes itnecessary to detect partial discharge reliably before the entire circuitbreakdown thereby to prevent such breakdown in advance. From thisbackground, there have been examined methods for detecting partialdischarge which may occur not only in a gas insulating device but alsoin any insulated device.

Of these, there is a method of detecting electromagnetic waves which aregenerated as a result of partial discharge, disclosed in Japanese PatentLaid-Open No. 107174/1989. By this method, there is provided a diagnosissystem in which input signals containing many radio frequency bandcomponents, received by an antenna provided in an insulated device, areexpanded in intensity for every frequency by a spectral analyzer, sothat only the presence/absence of partial discharge is detected based onthe distribution pattern and level. Another diagnosis system isdisclosed in Japanese Patent Laid-Open No. 260868/1995, in which thepresence/absence of partial discharge and the type of defect are judgedfrom the distribution and intensity of such a spectrum such that periodparameters such as the voltage phase angle are given to the intensity ofa fixed frequency in the intensity spectrum expanded by the spectralanalyzer.

SUMMARY OF THE INVENTION

An object of the present invention is to provide an insulated devicediagnosing system and a partial discharge detecting method, which candetect partial discharge accurately even for a different structure andcircuitry of a device, and for a different place where partial dischargeoccurs.

In order to achieve the above-specified object, according to the presentinvention, there is provided an insulated device diagnosing systemcomprising: an antenna provided in an insulated device; a patterngenerator for receiving a partial discharge signal from the antenna andpreparing detection data such that periodic elements are given to aplurality of specific frequencies; a neuro computer or a finger printingmethod operation unit for operating the detection data prepared by thepattern generator; and a judgment unit for diagnosing the extent ofabnormality, the deterioration, or the lifetime of the device from theoperation result of the operation unit. Moreover, the distribution ofthe frequency components of the detection signal is also measured forspecifying the specific frequencies to be detected. The insulated deviceis a gas insulated breaker, and when the partial discharge signalscoming from a plurality of antennas provided at different positions inthe gas insulated breaker are individually measured synchronously, thepartial discharge is located from the spectral pattern of the detectiondata between the same frequencies or from the intensity ratio.

According to the present invention, moreover, there is provided apartial discharge detecting method comprising the steps of: inputting apartial discharge signal from an input terminal; preparing detectiondata which are given periodic elements at a plurality of specificfrequencies of the partial discharge signal; and diagnosing the extentof abnormality, deterioration or lifetime of the device from the patternor intensity of the prepared detection data.

There is further provided a partial discharge detecting methodcomprising the steps of: inputting a partial discharge signal from aninput terminal; determining the intensity in which the partial dischargesignal is expanded for each frequency by an FFT or a spectral analyzerto select a plurality of specific frequencies having high intensities,detecting the intensity of each frequency of the partial dischargesignal to select a plurality of specific frequencies of which theintensities exceed a predetermined value, or selecting the frequencyhaving the highest intensity from the plural specific frequencies;preparing detection data, which are given periodic elements at aspecific frequency selected; and processing at least one of thedetection data or displaying the same on a screen to detect the partialdischarge.

There is further provided a partial discharge detecting methodcomprising the steps of: inputting a partial discharge signal from aninput terminal; preparing detection data such that a plurality ofspecific frequencies of a partial discharge signal are given periodicelements; preparing sampling data by differentiating either averageddata averaged from detection data of different frequencies or known datafrom the respective detection data, or by differentiating theintensities of the detection data which are detected by antennasprovided in different positions, between identical frequencies; anddiagnosing the extent of abnormality, the deterioration or the lifetimeof the device from the pattern or intensities of the prepared samplingdata.

Moreover, the extent or kind of abnormality, the deterioration or thelifetime of the device is diagnosed by processing the detection data bya neuro or a finger printing method.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram showing the construction of an insulated devicediagnosing system of one embodiment of the present invention;

FIG. 2 is a diagram showing the construction of a modification of theinsulated device diagnosing system shown in FIG. 1;

FIG. 3 is a diagram showing the construction of a modification of theinsulated device diagnosing system shown in FIG. 1;

FIG. 4 is a diagram showing the construction of a modification of theinsulated device diagnosing system shown in FIG. 1;

FIG. 5 is a diagram showing the construction of an insulated devicediagnosing system of another embodiment of the present invention;

FIG. 6 is a diagram showing the construction of a modification of theinsulated device diagnosing system shown in FIG. 5;

FIG. 7 is a diagram showing the construction of an insulated devicediagnosing system of another embodiment of the present invention;

FIG. 8 is a diagram showing a construction of a modification of theinsulated device diagnosing system shown in FIG. 7;

FIG. 9 is a diagram showing the construction of an insulated devicediagnosing system of another embodiment of the present invention;

FIG. 10 is a diagram showing the construction of an insulated devicediagnosing system of another embodiment of the present invention;

FIG. 11 is a diagram for explaining the principle of measurement;

FIG. 12 is a diagram showing the construction of a modification of theinsulated device diagnosing system shown in FIG. 10;

FIG. 13 is a diagram showing the construction of an insulated devicediagnosing system of another embodiment of the present invention;

FIG. 14 is a diagram showing the construction of an insulated devicediagnosing system of another embodiment of the present invention;

FIG. 15 is a diagram showing the construction of a modification of theinsulated device diagnosing system shown in FIG. 14;

FIG. 16 is diagrams illustrating an example of partial discharge due toa conductive foreign matter;

FIG. 17 Illustrates examples of a partial discharge spectrum when aspacer cracks and separates;

FIG. 18 is a diagram illustrating the noise level when electromagneticwaves in the device are measured; and

FIG. 19 illustrates the intensity distributions with respect to voltagephase angles and the kinds of defect.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

As shown in FIG. 1, an insulated device diagnosing system of the presentembodiment is constructed to comprise: an antenna 1 for receivingelectromagnetic waves generated from partial discharge, provided in aninsulated device such as a gas-insulated device, a transformer or acable; an amplifier 2 for receiving and amplifying the signal comingfrom the antenna I; a synchronizing element signal generator 4 forgenerating a synchronizing element signal; a plurality of spectralanalyzers 3a-3c for receiving the signal of the synchronizing elementsignal generator 4 and the signal amplified by the amplifier 2, toperform frequency analysis at specific frequencies; a pattern generator5 for generating a pattern which is synchronized with time by thesynchronizing element signal at the plural analyzed frequencies, i.e., apattern which has an intensity distribution of a specific frequency withrespect to a voltage phase angle; a pattern comparator 6 for comparingthe patterns which are produced by the pattern generator 5; and ajudgment unit 7 for making a judgment on the basis of the result of thepattern comparator 6. Here, the frequencies are fixed differentfrequencies determined by inputting signals such as pseudo pulses inadvance to the device and by measuring them. The pattern generator 5generates a pattern to which are added the synchronizing element and thespectral intensity by superposing the sinusoidal waveform as thesynchronizing element and the specific analyzed frequencies.

With this construction, the detection data having time elements can besynchronously prepared during the operation, so that the signal of thepartial discharge can be discriminated from noise by comparing thepattern of the detected data at each frequency with the fundamentaldata. Specifically, the frequency distribution and magnitude of theelectromagnetic waves generated by partial discharge are changed by thecircuitry of a power device or the location of the partial discharge.Since the electromagnetic waves are compared for the specificfrequencies, however, the noise and the signal of the partial dischargecan be discriminated from each other because correlation can be achievedwith the patterns. Moreover, the lifetime up to dielectric breakdown canbe estimated from the intensity of the detection data obtained.

FIG. 2 is a diagram showing a construction of an insulated devicediagnosing system of a modification of the embodiment shown in FIG. 1.In the modification, the portion for the pattern comparison is processedby a neuro computer 8. This neuro computer can make judgment about evenan unknown pattern highly precisely and is suited for the diagnosis bygiving it teacher data in advance.

FIG. 3 is a diagram showing a construction of a modification of theinsulated device diagnosing system of the embodiment shown in FIG. 1. Inthe modification of FIG. 3, the pattern comparison is performed by afinger printing method (hereinafter referred to also as the FP method).As shown in FIG. 3, the insulated device diagnosing system is equippedwith a memory unit 10 for storing a database and an FP method operationunit 9 connected with the memory unit 10. In this example, moreover, onespectral analyzer 3 is used for one antenna 1, as shown in FIG. 4. Inthis method, the frequency analysis is made at a plurality of specificfrequencies by varying the fixed frequency of the spectral analyzer atpreset time intervals by the signal of the synchronizing element signalgenerator 4 and by a control unit 11. By this method, the measurement ofa frequency f2 cannot be performed at the time of measuring a fixedfrequency f1, so that there is an uncertain element in partial dischargevarying with time. However, the method is advantageous in that thenumber of spectral analyzers can be reduced, thereby providing aneconomically advantageous aspect and making the measuring systemcompact.

As in this example, the FP method is free from the learning which isnecessary for the neuro computer, so that the software can be easilydeveloped. On the other hand, the FP method is inferior to the neurocomputer in the judgment precision for an unknown pattern.

For the insulated device diagnosing system of the present embodimentthus constructed, not only the kind of defect in the device can bedetected with a high sensitivity, but also the situation of the partialdischarge can be grasped with a high precision, and hence the extent orkind of deterioration, lifetime or abnormality of the device can bediagnosed highly sensitively and precisely.

Another embodiment of the present invention will be described withreference to FIGS. 5, 6. FIG. 5 is a diagram showing the construction ofan insulated device diagnosing system of the embodiment, and FIG. 6 is adiagram showing the construction of a modification of the insulateddevice diagnosing system.

In the present embodiment, as shown in FIG. 5, the intensitydistributions at a plurality of predetermined frequencies with respectto the voltage phase angle and the spectral distributions for frequencydistributions are combined to detect partial discharge. Specifically,the signal of the synchronizing element signal generator 4 is added notonly to the spectral analyzers 3A-3C in FIG. 1 but also to a spectralanalyzer 3d so that the spectral distribution can be synchronouslymeasured by the spectral analyzer 3d. With this construction, not onlythe intensity distributions at the specific frequencies with respect tothe voltage phase angle but also the spectral distributions can besimultaneously measured, imparting the advantages of the measuringmethods.

FIG. 6 shows a modification of FIG. 5, in which one spectral analyzer 3is used for each antenna 1, as described with reference to FIG. 4, sothat the frequency analysis may be performed by varying the fixedfrequency of the spectral analyzer 3 and the spectral distribution atpreset time intervals by the signal of the synchronizing element signalgenerator 4 and by the control unit 11. This modification also haseffects similar to those of the description of FIG. 4.

Another embodiment of the present invention will be described withreference to FIGS. 7 and 8. FIG. 7 is a diagram for illustrating a datapreparing method, and FIG. 8 is a diagram showing a construction of aninsulated device diagnosing system of the present embodiment.

In the present embodiment, as shown in FIG. 7, averaged data andsampling data are prepared from the detected data for different specificfrequencies. As illustrated at the lefthand side of FIG. 7, morespecifically, the averaged data are prepared by adding and averaging thedata of frequencies f1, f2 and f3, and the sampling data are prepared bydifferentiating the averaged data from the data of the frequency f2, forexample.

The averaged data are the averaged intensity distributions of thedetected data with respect to different specific frequencies. Whennoises are present only at the frequency f3, for example, it is possibleto prepare the data in which the noise is apparently decreased.Moreover, the intensity distribution of the signal is also averaged sothat the matching with the fundamental data of partial discharge can befacilitated. If this matching with the pattern of the fundamental datais difficult, it may be improved depending upon the frequency byreferring to the sampling data, so that the diagnosing precision ofpartial discharge can be improved.

A specific example of the construction is shown in FIG. 8, in which thesignal from the antenna 1 is inputted to and amplified by the amplifier2 and is fed to the spectral analyzer 3. To this spectral analyzer 3,there are connected the synchronizing element signal generator 4 and thecontrol unit 11. The output of the spectral analyzer 3 is connected toan averaged data generator 12 and a differentiator 14, which areconnected to a memory unit 13. The differentiator 14 is connected to apattern recognition unit 15 such as a neuro computer, which is furtherconnected to the judgment unit 7.

In the insulated device diagnosing system thus constructed, the settingof the spectral analyzer 3 is varied at preset time intervals by thecontrol unit 11, and the measured signal is inputted to the averageddata generator 12 to prepare the averaged data, so that the result isstored in the memory unit 13. Next, the averaged data are differentiatedfrom the detection data obtained from spectral analyzer 3, to preparethe sampling data. The partial discharge is measured by inputting theaveraged data and the sampling data to the pattern recognition unit 15so that they may be processed.

Another embodiment of the present invention will be described withreference to FIG. 9. FIG. 9 is a diagram showing the construction of theinsulated device diagnosing system of the present embodiment.

The insulated device diagnosing system of the present embodiment is soconstructed as to comprise: an amplifier 2 connected to an antenna 1; anFFT 16 connected in parallel with the amplifier 2; a differentiator 14connected to the FFT 16 and to the spectral analyzer 3 through a controlunit 11; a pattern recognition unit 15 of a neuro computer or the FPmethod connected to the spectral analyzer 3; and the judgment unit 7connected to the pattern recognition unit 15. In the present embodiment,both the spectral analyzer 3 and the FFT 16 are employed, a plurality offrequencies having high spectral intensities are selected by anoperation unit, and the detection data are prepared by varying thesetting of the spectral analyzer 3 at preset time intervals. Thus, therange of the frequencies to be selected can be widened, and thefrequency to be set can be optimized for the situation of the partialdischarge; therefore the partial discharge can be detected highlysensitively and precisely.

Another embodiment of the present invention will be described withreference to FIGS. 10 to 12. Fig. 10 is a diagram showing theconstruction of the insulated device diagnosing system of the presentembodiment; FIG. 11 is a diagram illustrating the principle ofmeasurement; and FIG. 12 is a diagram showing the construction of aninsulated device diagnosing system of a modification of FIG. 10.

In the insulated device diagnosing system of the present embodiment, asshown in FIG. 10, there are provided a plurality of antennas 1A-1C, towhich spectral analyzers 3A-3C are respectively connected throughamplifiers 2A-2C. Each spectral analyzer is connected to a synchronizingelement signal generator 4, which is connected to a pattern generator 5for preparing synchronized intensity distribution patterns of specificfrequencies with respect to voltage phase angles. To this patterngenerator 5, moreover, there is connected an operation unit 9 which inturn is connected to a judgment unit.

In the present embodiment, the antennas 1 are used to synchronize themeasurements at the individual antennas 1 so that not only the parts tobe insulation-diagnosed but also the discharge parts can be located, aswill be described with reference to FIG. 11. For example, theelectromagnetic waves propagated in the SF₆ gas are different inattenuation depending on the frequency, as illustrated in FIG. 11, sothat the partial discharge can be located by determining the ratios ofthe detection data of the same frequency, collected from the antennas. Amore distant partial discharge can be located with a higher precision byusing the detection data for frequencies.

FIG. 12 shows a diagnosing system in which the FP method is employed butpartial discharge is not located, unlike the embodiment shown in FIG.10. Thus, the system can be simplified to hold down the cost of thesystem.

Another embodiment of the present invention will be described withreference to FIG. 13. FIG. 13 is a diagram showing the construction ofan insulated device diagnosing system of the present embodiment, andshows an insulated device diagnosing system applied to a gas insulatedbreaker.

In the insulated device diagnosing system of the present embodiment, asshown in FIG. 13, an antenna 1 provided in a gas insulated breaker isconnected through an amplifier 2 to a spectral analyzer 3, so that thefrequency analysis is made by changing the fixed frequency of thespectral analyzer 3 and the spectral distribution at preset timeintervals by a control unit 11 connected to the spectral analyzer 3. Thepattern of the intensity distribution of specific frequencies withrespect to the voltage phase angle is prepared by a pattern generator 5and is processed by a processing system 16. After this, the processedpattern is inputted to a neuro computer 9a and an FP method operationunit 9b, which are respectively connected to memory units 10a and 10bthat store databases. The spectral distribution made by a spectraldistribution generator 5b is inputted to judgment unit 7a. All theoutputs of the neuro computer 9a, the FP method operation unit 9b andthe judgment unit 7a are inputted to a judgment unit 7b.

Thus, the present embodiment judges in combination both the result thatthe pattern of the intensity distribution of the specific frequency withrespect to the voltage phase angle is operated by the neuro computer 9aand the FP method operation unit 9b, and the result of the judgment fromthe frequency spectral distribution, so that an insulation diagnosis ofhigher precision can be made. As a result, the present embodiment iseffective in major substations that especially require high reliability.

Another embodiment of the present invention will be described withreference to FIGS. 14 and 15. FIG. 14 is a diagram showing theconstruction of the insulated device diagnosing system of the presentembodiment, and FIG. 15 shows a modification of the insulated devicediagnosing system.

The insulated device diagnosing system of the present embodiment makesthe specific frequencies variable although it is constructed as in theembodiment shown in FIG. 14. As a result, the present embodiment isadvantageous in that a plurality of more appropriate specificfrequencies can be selected for various kinds of partial discharge. Inthe example of FIG. 16, the partial discharge can be detected bypreparing the detection data given a periodic element for such one ofthe selected frequencies that the frequency has the largest differencebetween the detected intensity and the noise, and by displaying thedetection data on a screen or by processing the same. By using thismethod, it is possible to reduce the number of detection data when thestate of partial discharge is automatically monitored for a long time.As a result, the capacity of the memory unit can be reduced to prolongthe maintenance interval and to hold down the cost.

By selecting a plurality of specific frequencies to prepare thedetection data, according to the present invention, it is possible tohighly precisely detect electromagnetic waves which are generated frompartial discharge varying with the kind and location of the partialdischarge and the circuitry of the power device, and to judge the stateof the partial discharge highly precisely from the spectral pattern andthe intensity between the individual frequencies.

What is claimed is:
 1. An insulated device diagnosing system comprising:an antenna provided in an insulated device; a pattern generator forreceiving a partial discharge signal from said antenna, said partialdischarge signal resulting from electromagnetic wave energy of a partialdischarge received by said antenna, and preparing detection data fromthe partial discharge signal such that periodic elements are given to aplurality of specific frequencies of the partial discharge signal; aneuro computer or a finger printing method operation unit for processingthe detection data prepared by said pattern generator; and a judgmentunit for diagnosing an extent of abnormality, a deterioration, orlifetime of said insulated device from the operation result of saidneuro computer or finger printing method operation unit.
 2. An insulateddevice diagnosing system according to claim 1, wherein a distribution offrequency components of the detection signal is also measured forspecifying the specific frequencies to be detected.
 3. An insulateddevice diagnosing system according to claim 2, wherein said insulateddevice is a gas insulated breaker, wherein said partial dischargesignals coming from a plurality of antennas provided at differentpositions in said gas insulated device are measured synchronously, andwherein the partial discharge is located from the spectral patterns orintensity ratios of said detection data between the same frequencies. 4.An insulated device diagnosing system according to claim 1, wherein saidinsulated device is a gas insulated breaker, wherein said partialdischarge signals coming from a plurality of antennas provided atdifferent positions in said gas insulated device are measuredsynchronously, and wherein the partial discharge is located from thespectral patterns or intensity ratios of said detection data between thesame frequencies.
 5. A partial discharge detecting method comprising thesteps of: inputting a partial discharge signal of an insulated devicefrom an input terminal, the partial discharge signal resulting fromelectromagnetic wave energy of a partial discharge; preparing detectiondata from the partial discharge signal which are given periodic elementsat a plurality of specific frequencies of the partial discharge signal;and diagnosing an extent of abnormality, deterioration, or lifetime ofthe insulated device from a pattern or intensity of the prepareddetection data.
 6. A partial discharge detecting method according toclaim 5, wherein the extent of abnormality, the deterioration, or thelifetime of the insulated device is diagnosed by processing saiddetection data by a neuro computer method or by a finger printingmethod.
 7. A partial discharge detecting method comprising the steps of:inputting a partial discharge signal of an insulated device from aninput terminal, the partial discharge signal resulting fromelectromagnetic wave energy of a partial discharge; determining theintensity in which said partial discharge signal is expanded for eachfrequency by an FFT or a spectral analyzer to select a plurality ofspecific frequencies from frequencies having high intensities, detectingthe intensity of each frequency of said partial discharge signal toselect a plurality of specific frequencies, of which the intensitiesexceed a predetermined value, or selecting the frequency having thehighest intensity from the specific frequencies; preparing detectiondata from the partial discharge signal which are given periodic elementsat a specific frequency selected of the partial discharge signal; andprocessing at least one of said detection data or displaying at leastone of the detection data on a screen to detect partial discharge.
 8. Apartial discharge detecting method according to claim 7, wherein anextent or kind of abnormality, deterioration, or lifetime of theinsulated device is diagnosed by processing said detection data by aneuro computer method or by a finger printing method.
 9. A partialdischarge detecting method comprising the steps of: inputting a partialdischarge signal from an input terminal, the partial discharge signalresulting from electromagnetic wave energy of a partial discharge;preparing detection data from the partial discharge signal such that aplurality of specific frequencies of the partial discharge signal aregiven periodic elements; preparing sampling data by differentiatingeither averaged data averaged from detection data of differentfrequencies or known data from the individual detection data, or bydifferentiating the intensities of the detection data detected byantennas provided in different positions of the insulated device,between identical frequencies; and diagnosing an extent of abnormality,deterioration, or lifetime of the insulated device from the pattern orthe intensities of the prepared sampling data.
 10. A partial dischargedetecting method comprising the steps of: preparing detection data givenperiodic elements from one of a plurality of specific frequencies of apartial discharge signal, the partial discharge signal resulting fromelectromagnetic wave energy of a partial discharge; and processing saiddetection data or displaying the detection data on a screen to detect apartial discharge.